|The authors responded to all my comments and the manuscript is in much better shape now to be published. I only have a few minor comments left.|
Please go through all references and make sure they are all included as I found some missing ones (below).
Comments by line numbers (with respect to the red-lined document)
296-297. Can you clarify this a bit more? You mean that the prevailing winds are from the west so OOA increases to the east because it takes time for OOA to form? Do you see similar gradients in Ozone? (if its following the evolution of photochemistry then you should see it behaves similarly as Ozone)
428-429 (and 559-560). Unless there is a study describing such mechanism, I think stating that it’s based on high NOx levels is too much of an assumption. On polluted sites/cities many other pollutants are high which could also be involved in SOA production. For instance, aqueous-phase SOA turning freshly emitted VOC into SOA, that is a well-established mechanism and is feasible due to the higher humidity in winter vs summer, could be a more likely mechanism to blame rather than hypothesize a new one.
444-446. What do you mean by “base-case OA scheme in PMCAMx”? Is aqueous SOA formation included in other PMCAMx configurations? If it is included, why didn’t you performed a sensitivity simulation with aqueous SOA formation? This sentence is confusing after you stated above that there is definitely something missing in the model configuration you use.
483. I think this should be: “The model presents a delay in the timing of the morning rise of the boundary layer …”. Using “underestimation” is too vague, as it could refer to a delay or to a slower growth rate. Morning growth rate seems well represented in the model.
483-485. Given the delay on the PBL growth, I encourage the authors to check in their model configuration and analysis for any shift in time that could have gone unnoticed and that could be generating this apparent delay. Many plots are in local time, so please check that the daylight savings was applied correctly when reading model output and observations, and that the emission cycle was included correctly into the model with respect to daylight savings. Also, PBL height in WRF is outputted at the valid time and it is an instantaneous value, while the observations might be an average for an hour, so they should be valid at the center time of the averaging window.
572. Please add a reference to the statement “meat grilling is one known important source of COA”
Line 444-445. Murphy et al., 2011, 2012, references are not in the reference list. You could also add a more recent aqueous-phase SOA modeling study: Knote, C., Hodzic, A., Jimenez, J. L., Volkamer, R., Orlando, J. J., Baidar, S., Brioude, J., Fast, J., Gentner, D. R., Goldstein, A. H., Hayes, P. L., Knighton, W. B., Oetjen, H., Setyan, A., Stark, H., Thalman, R., Tyndall, G., Washenfelder, R., Waxman, E., and Zhang, Q.: Simulation of semi-explicit mechanisms of SOA formation from glyoxal in aerosol in a 3-D model, Atmos. Chem. Phys., 14, 6213-6239, doi:10.5194/acp-14-6213-2014, 2014.
484. I think this should be “BC overprediction”
Table 2: There are “,”s missing after when you switch to the next line but within the same OA component (after COA for the first two components, after HOA and after BBOA)
Fig. S6. The back-trajectories for Feb 10 are not fully contained in the plot, please expand the visualization domain so they are all contained like in the other panels.